1. Field of the Invention
The present invention relates to a liquid crystal display device, and in particular to a liquid crystal display device comprising an alignment film which has been imparted with an orientation regulating force through a photo-alignment treatment. Moreover, the present invention also relates to an electronic apparatus incorporating such a liquid crystal display device.
2. Description of the Related Art
In recent years, liquid crystal display devices have been used in OA devices such as personal computers and AV devices such as camcorders, on the strength of being thin and consuming little power.
A liquid crystal display device performs displaying by utilizing optical anisotropy of liquid crystal molecules, and therefore the orientation directions of the liquid crystal molecules must be controlled with alignment films. As alignment films, films which are formed of a polymer material such as polyimide or polyvinyl alcohol and which have been subjected to a rubbing treatment are commonly used.
However, when alignment films which have been subjected to a rubbing treatment are used, there are problems in that orientation defects may occur due to foreign matter which emerged during the rubbing, or switching elements (e.g., TFTs) which are provided on the substrate may be destroyed by the static electricity which is generated during the rubbing.
In order to solve these problems, a photo-alignment treatment (photo-alignment technique) has been proposed. A photo-alignment treatment is disclosed in Japanese Laid-Open Patent Publication No. 2-277025 (Patent Document 1) or Japanese Laid-Open Patent Publication No. 4-303827 (Patent Document 2), for example. A photo-alignment treatment is a technique where an alignment film which is formed of a compound including a photoreactive functional group is irradiated with polarized ultraviolet light in order to allow the molecules in the alignment film to undergo an anisotropic chemical reaction, whereby the alignment film acquires an orientation regulating force. Recently, there have also been developed a method where non-polarized ultraviolet light is used for the irradiation, instead of polarized ultraviolet light.
However, when a liquid crystal display device incorporating alignment films which have been imparted with an orientation regulating force through a photo-alignment treatment (hereinafter referred to as “photo-alignment films”) are used for long hours, the alignment may be disturbed or the voltage retention rate may be lowered. Thus, a liquid crystal display device incorporating photo-alignment films lacks in reliability.